NASA Visualizes the Dance of a Melting Snowflake

A new video features
a visualization of the first three-dimensional numerical model of melting
snowflakes in the atmosphere, developed by scientist Jussi Leinonen of NASA's
Jet Propulsion Laboratory in Pasadena, California. A better understanding of how
snow melts can help scientists recognize the signature in radar signals of heavier,
wetter snow -- the kind that breaks power lines and tree limbs -- and could be
a step toward improving predictions of this hazard.

Snowflake
research is one of many ways that NASA studies the frozen regions of Earth,
collectively known as the cryosphere.

This visualization is based on the first three-dimensional numerical model of melting snowflakes in the atmosphere, developed by scientist Jussi Leinonen of NASA's Jet Propulsion Laboratory in Pasadena, California. A better understanding of how snow melts can help scientists recognize the signature in radar signals of heavier, wetter snow -- the kind that breaks power lines and tree limbs -- and could be a step toward improving predictions of this hazard.

Leinonen's
model reproduces key features of melting snowflakes that have been observed in
nature. First, meltwater gathers in any concave regions of the snowflake's
surface. These liquid-water regions then merge to form a shell of liquid around
an ice core, and finally develop into a water drop. The modeled snowflake shown in the video
is less than half an inch (one centimeter) long and composed of many individual
ice crystals whose arms became entangled when they collided in midair.

Some of the most remote places on Earth are showing signs of change, with potentially global impacts. In 2018, NASA is scheduled to launch two new satellite missions and conduct an array of field research that will enhance our view of Earth's ice sheets, glaciers, sea ice, snow cover and permafrost. Collectively, these frozen regions are known as the cryosphere. Over the course of the year NASA will share an inside look at what the agency is doing to better understand this critical component of our home planet.

Leinonen said
he became interested in modeling melting snow because of the way it affects
observations with remote sensing instruments. A radar "profile" of
the atmosphere from top to bottom shows a very bright, prominent layer at the
altitude where falling snow and hail melt -- much brighter than atmospheric
layers above and below it. "The reasons for this layer are still not
particularly clear, and there has been a bit of debate in the community," Leinonen
said.

Simpler models
can reproduce the bright melt layer, but a more detailed model like this one can
help scientists understand it better, particularly how the layer is related to the
type of melting snow and the radar wavelengths used to observe it.

A paper on
the numerical model, titled "Snowflake melting simulation using smoothed
particle hydrodynamics," recently appeared in the Journal of Geophysical
Research -Atmospheres.